A combined LEED/RHEED Auger study of oxygen adsorption on the W(112) surface

LEED, RHEED and Auger spectroscopy have been used to study the adsorption of oxygen on to a clean and carbon contaminated (112) face of tungsten. At room temperature all the features reported previously were observed together with a p(1 × 4) surface structure which appeared at an exposure of about 1. 4L just before the formation of the p(1 × 2). Previously a p(1 × 4) structure has been reported only after heating to 2000K. RHEED showed this p(1 × 4) structure clearly; using LEED, the structure was difficult to distinguish. This appears to confirm suspicions that in some situations involving gas adsorption, RHEED has a greater sensitivity than LEED. Possibly most of these situations involve, as does the present p(1 × 4) structure, monolayer islands where the differing coherence widths of the RHEED and LEED beams account for the differing sensitivities. Carbon on the (112) surface also appears to exist as thin islands, either of the previously reported c(6 × 4) structure, or in smaller amounts, on a surface showing (1 × 1) symmetry. Removal of all carbon by heat treatment alone was found to be impossible in a reasonable time and heating in oxygen was necessary. Oxygen adsorption on a carbon contaminated surface did not give rise to any new structures but rather a reduction in the visibility/formation of the clean surface/oxygen structures.     

Adsorption of polymers at the solution–solid interface. V. Styrene–methyl methacrylate copolymers on carbon

The adsorption of a series of block and random styrene–methyl methacrylate copolymers on an animal charcoal and on Graphon has been studied. On charcoal, adsorption decreases with increase of molecular weight because of the inability of larger coils to penetrate into the adsorbent. An analysis is presented which requires that coils undergo considerable distortion on adsorption in pores. The adsorption of random copolymers on Graphon is also in reverse order of molecular weight; this effect may be due to particle bridging leading to the formation of interparticle “pores.” The relative affinity of the styrene and methyl methacrylate residues is different on charcoal and Graphon, respectively; on both surfaces, however, relatively few of the more active residues are required for adsorption. Block and random copolymers are adsorbed to different extents which depend on the nature of the adsorbent surface.     

Vibrational resonances below 5 MeV in the fission of 240Pu

Using the ²³⁹Pu(d, pf) reaction, the next lower K^π = 0⁺ vibrational resonance below 5 MeV in the deformed potential of ²⁴⁰Pu was located at 4.55 MeV. The resultant spacing of fission vibrations near 5 MeV in the second minimum is 500 keV. A resonance at 4.70 MeV is interpreted as the K^π = 0^? vibration coupled to the 4.55 MeV K^π = 0⁺ state, which yields E(K^π = 0^?) = 150 keV relative to the ground state of the second minimum.     

Ionization and electron capture in neon K vacancy production from NNe collisions

Our measurements of Ne K and N K X-ray cross sections for N^{3+,4+,5+,6+,7+,} ions incident on a thin Ne target at energies from 9 to 54 MeV indicate that charge exchange plays a minor role compared to ionization in producing Ne K vacancies over that energy range.     

A sensitive technique for detecting chemical changes by AES

The measurement of Auger currents and their associated peak to peak heights from the first derivative spectra has provided the basis for an analysis of the various stages of nitric oxide absorption onto a W(110) surface at room temperature. This chemisorption system is a test case for the method since the nitrogen and oxygen KLL Auger spectra in first derivative form look similar at all stages of adsorption. The results indicate that the method is sensitive to chemical changes in the adsorbate to an extent comparable with XPS.     

Polarization of 22 MeV neutrons elastically scattered from liquid tritium

The asymmetries from elastic scattering of 22.1 MeV incident neutrons was measured for 11 laboratory angles between 40° and 118.5°. The extrema are −60% at 85° (lab) and +98% at 110° (lab).